Background and Objectives: Right coronary artery (RCA) ostial stent implantation is one of the risk factor of instent restenosis (ISR). In right coronary ostial stenting, The role of drug eluting stents (DES) is not evaluated clearly. Thus, this study investigated the comparison of angiographic outcomes of patients with right coronary ostial stenting between Sirolimus eluting stents (SES) and Paclitaxel eluting stents (PES), and the risk factor of ISR in right coronary DES implantation. Subjects and Methods: From December 2001 to October 2007, we reviewed 61 patients who underwent percutenous coronary intervention in right coronay ostial lesions using SES (n=38) or PES (n=23), and followed up coronary imaging by coronary angiography (CAG) in KOrean Multicenter Angioplasty TEam (KOMATE) registry. We compared the ISR rate between SES and PES, and investigated the predictor of ISR at RCA ostial stenting. Results: Twelve cases of ISR after 62 RCA ostial SES or DES implantation were identified during 13 짹8 months [SES vs. PES: 4 cases (10.5%) vs. 8 cases (34.8 %), p=0.043) The independent predictors for right ostial ISR estimated by multivariate logistic analysis were PES implanting (OR=5.15, 95 % C.I.: 1.24-21.34) and stent which had diameter > 3.0 mm (OR=0.168, 95% C.I.: 0.03-0.91) controlling the known risk factors of ISR. Conclusions: The PES implantation and less than 3 mm stent diameter were risk factors for ISR of RCA ostial lesion. Thus, SES implantation might be superior to PES implantation for reducing the ISR at RCA ostial lesion